Steel and aluminum are widely used to fabricate structural components of automobiles and aircraft. Although these materials offer high impact resistance and rigidity, they suffer from various shortcomings. For example, aluminum is light weight but costly. Steel has a low cost but is heavy and not corrosion resistant. Neither material is thermoformable. A need exists for a material, specifically in sheet form which is inexpensive, lightweight, corrosion resistant and thermoformable.
An apparatus for continuously fabricating lightweight structural panels is disclosed in U.S. Pat. No. 4,897,146. This patent teaches heating a single layer core sheet to a temperature at which it is plastically deformable and passing it through a corrugating machine. The corrugated sheet is then passed through a compression nip and is adhered to superposed sheets of other similar or identical material to produce a panel. While the corrugated panel product is useful for many applications, it does not offer the impact resistance and rigidity necessary for automotive and aircraft applications.
Methods of on-line lamination of polyester structures are taught in U.S. Pat. No. 4,544,586. Ultraviolet radiation absorbing layers are laminated to a polyester core structure. Unfortunately, these materials, while resistant to ultraviolet degradation, fail to exhibit the properties necessary for automotive door, hood and side panel applications.